AV1 to M4B Converter

Convert AV1 to M4B: Read This First

This page converts an .av1 file to .m4b — the MPEG-4 audiobook container Apple Books and dedicated audiobook apps file as a book and resume from your last position. There is one honest catch you should know before uploading: a bare .av1 file is a raw AV1 video bitstream that holds only picture, no sound, so extracting audio from a true .av1 usually gives you a silent or empty M4B. AV1 is a video-only codec released by the Alliance for Open Media in 2018; the audio that goes with AV1 video lives in a container (MP4, WebM, or MKV), never in the raw stream. If your goal is the soundtrack, you almost certainly want to convert that container instead — the walk-through below shows exactly how.

How to Convert AV1 to M4B

1. Upload Your AV1 File: Drag and drop your .av1 file onto the page, or click "Add Files" to browse. You can queue several files and convert them in one batch with the same settings.
2. Set the Quality Preset: M4B stores AAC audio, so the output is AAC by design. Leave Quality Preset on "Very High (Recommended)" for a clean result, or open File Compression to choose a Custom Bitrate, Constant Bitrate, or a Specific file size for a long recording.
3. Adjust Audio (Optional): Use Audio Channel to fold a stereo source to mono, Audio Sample Rate to downsample speech, or Trim to keep only part of the file.
4. Convert and Download: Click "Convert" and save your .m4b. Files upload over an encrypted connection, convert on our servers, and are deleted automatically a few hours later. No sign-up, no watermark.

Walk-through: Why a Raw AV1 File Has No Sound to Extract

AV1 is purely a video coding format. The raw bitstream — the kind of file that carries a .av1 (or .obu) extension — packetizes everything into Open Bitstream Units (OBUs), and the AV1 specification defines those units for coded video only. There is no provision for an audio track in the raw stream. When you watch an AV1 video with sound, that audio is a separate track (commonly Opus or AAC) multiplexed alongside the video inside a container such as MP4, WebM, or Matroska (MKV).

That distinction decides which tool you actually need:

• If you genuinely have a raw .av1 bitstream, there is no audio inside it, so the M4B comes out empty or silent. That is not a tool bug — there is simply no sound in the source.
• If your "AV1 file" is really an .mp4, .webm, or .mkv whose video happens to use the AV1 codec, the soundtrack you want is in that container. Convert it directly with MP4 to M4B, WebM to M4B, or MKV to M4B and you will get the audio. People often call those "AV1 files" loosely because the video codec is AV1 — but the extension on disk is what tells you which tool to use.

There is a second thing to know even when you do have audio: M4B gives you the audiobook container, not automatic chapter markers. A single source file becomes one flat track inside an audiobook wrapper. Resume-position still works; per-chapter navigation does not unless chapters already existed in the source.

Common Errors and How to Fix Them

• "My M4B is silent or empty" — Expected for a true raw .av1 bitstream: it contains no audio to extract. Convert the container that holds your AV1 video instead — MP4 to M4B, WebM to M4B, or MKV to M4B.
• "There are no chapters / it won't show a chapter list" — A single source file has no chapter data to carry over, so the output is a flat track inside an audiobook wrapper. Resume-position works; named chapters require a dedicated audiobook builder.
• "My player restarts instead of resuming" — Resume behavior depends on the player honoring the .m4b extension. Use Apple Books, VLC, or a dedicated audiobook app; a generic music player may treat it as a track and restart.
• "It won't open on my Android phone" — M4B plays natively on iOS and macOS. On Android, install a third-party audiobook player that supports M4B, since the stock player often won't.
• "I wanted to keep the video" — This is an audio target. To keep the picture, convert to a video format with AV1 to MP4 instead.

When This Doesn't Work

This tool can only write audio that actually exists in the source, and a genuine raw .av1 bitstream is video-only — so there is no soundtrack for it to produce. The realistic path to an M4B audiobook is to start from the container that carries both the AV1 video and its audio, using MP4 to M4B or WebM to M4B. It also makes one M4B from one file with audio controls only; it does not stitch multiple files into one book, author named chapter markers, or add cover art, so it is not a full audiobook-production tool. For a chaptered book built from several parts, produce per-chapter audio first and assemble it with a dedicated builder (Audiobook Binder, Chapter and Verse, or the m4b-tool command line). To split a long recording into pieces by time, run the audio through Audio Cutter.

Frequently Asked Questions

Why is my AV1-to-M4B output silent or empty?

Because a raw .av1 file is a video-only bitstream. AV1 is a video codec, and its raw Open Bitstream Unit stream carries no audio track at all — sound always rides in a container (MP4, WebM, MKV) alongside the AV1 video. With nothing to extract, the M4B comes out empty or silent. To get the soundtrack, convert the container file with MP4 to M4B or WebM to M4B.

My video uses AV1 but it's an MP4 — which tool do I use?

Use the tool that matches the file's actual extension on disk. If the file ends in .mp4, the audio is inside that MP4 container even though the video codec is AV1, so MP4 to M4B is the right choice. Use this AV1-to-M4B page only for true raw .av1 (or .obu) bitstreams — and those have no audio to extract.

Does converting AV1 to M4B add chapter markers to my audiobook?

No. M4B is the container Apple uses for audiobooks because it can hold chapter markers and a resume position, but those markers must already exist in the source or be authored by hand. A single source file becomes one flat track inside an audiobook wrapper — the resume position still works in apps like Apple Books and Bookplayer, but there are no named chapters. For genuine chapters you need a dedicated audiobook tool (Audiobook Binder on Mac, Chapter and Verse, or m4b-tool); no online converter generates chapters from a flat soundtrack.

What's the difference between M4B and M4A for this conversion?

They are the same MPEG-4 container holding the same AAC audio — the difference is the extension and how players treat it. M4B signals "audiobook," so audiobook apps track your listening position and surface chapters when present; M4A is treated as a normal music or podcast track. If you want resume behavior, choose M4B; for a plain AAC file use AV1 to M4A instead. For the most universal playback, AV1 to MP3 is the safer pick at the cost of resume support.

Can I play the M4B on Android or Windows?

Yes, with the right app. M4B plays natively on iOS and macOS. On Windows you can use VLC or iTunes; on Android you will typically need a third-party audiobook player that supports M4B, since stock players often do not. If you need a file that plays on nearly anything, AV1 to MP3 is the safer choice.

How are my files handled, and how long do you keep them?

Your file is uploaded over an encrypted (TLS) connection, processed on our servers, and the upload plus the converted M4B are deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public. In our testing, a genuine raw .av1 bitstream produces an M4B with no audible audio, which is the expected result for a video-only source; the practical limit on a long container-based recording is upload size and time over your own connection rather than any per-file feature cap.